Angled blade root

ABSTRACT

A blade root for a wind turbine rotor blade is disclosed. The blade root may generally comprise a substantially cylindrically shaped member extending lengthwise along a longitudinal axis and defining a planar end surface. Additionally, an angle may be defined between the planar end surface and a reference plane extending perpendicular to the longitudinal axis. The angle may be greater than 0 degrees and less than about 10 degrees.

FIELD OF THE INVENTION

The present subject matter relates generally to wind turbines and, moreparticularly, to an angled blade root for a wind turbine rotor blade.

BACKGROUND OF THE INVENTION

Wind power is considered one of the cleanest, most environmentallyfriendly energy sources presently available, and wind turbines havegained increased attention in this regard. A modern wind turbinetypically includes a tower, generator, gearbox, nacelle, and one or morerotor blades. The rotor blades capture kinetic energy from the windusing known airfoil principles and transmit the kinetic energy throughrotational energy to turn a shaft coupling the rotor blades to agearbox, or if a gearbox is not used, directly to the generator. Thegenerator then converts the mechanical energy to electrical energy thatmay be deployed to a utility grid.

To ensure that wind power remains a viable energy source, efforts havebeen made to increase energy outputs by modifying the size and capacityof wind turbines. One such modification has been to increase the lengthand surface area of the rotor blades. However, the magnitude ofdeflection forces and loading of a rotor blade is generally a functionof blade length, along with wind speed, turbine operating states, bladestiffness, and other variables. This increased loading not only producesfatigue on the rotor blades and other wind turbine components but mayalso increase the risk of a sudden catastrophic failure of the rotorblades, for example, when excess loading causes deflection of a bladeresulting in a tower strike.

Accordingly, a rotor blade configuration that allows for the use oflonger rotor blades without increasing the likelihood of a tower strikewould be welcomed in the technology.

BRIEF DESCRIPTION OF THE INVENTION

Aspects and advantages of the invention will be set forth in part in thefollowing description, or may be obvious from the description, or may belearned through practice of the invention.

In one aspect, the present subject matter discloses a rotor blade for awind turbine. The rotor blade may generally include a blade rootdefining a planar surface, a blade tip and a body extending between theblade root and the blade tip. The body may define a longitudinal axisand may include a pressure side and a suction side extending between aleading edge and a trailing edge. Additionally, an angle may be definedbetween the planar surface and a reference plane extending perpendicularto the longitudinal axis. The angle may be greater than 0 degrees andless than about 10 degrees.

In another aspect, the present subject matter discloses a wind turbine.The wind turbine may include a plurality of rotor blades. Each rotorblade may include a blade root defining a planar surface, a blade tipand a body extending between the blade root and the blade tip. The bodymay define a longitudinal axis and may include a pressure side and asuction side extending between a leading edge and a trailing edge.Additionally, an angle may be defined between the planar surface and areference plane extending perpendicular to the longitudinal axis. Theangle may be greater than 0 degrees and less than about 10 degrees.

In another aspect, the present subject matter discloses a blade root fora wind turbine rotor blade. The blade root may generally comprise asubstantially cylindrically shaped member extending lengthwise along alongitudinal axis and defining a planar end surface. Additionally, anangle may be defined between the planar end surface and a referenceplane extending perpendicular to the longitudinal axis. The angle may begreater than 0 degrees and less than about 10 degrees.

These and other features, aspects and advantages of the presentinvention will become better understood with reference to the followingdescription and appended claims. The accompanying drawings, which areincorporated in and constitute a part of this specification, illustrateembodiments of the invention and, together with the description, serveto explain the principles of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

A full and enabling disclosure of the present invention, including thebest mode thereof, directed to one of ordinary skill in the art, is setforth in the specification, which makes reference to the appendedfigures, in which:

FIG. 1 illustrates a perspective view of one embodiment of a windturbine;

FIG. 2 illustrates a perspective view of one embodiment a rotor blade inaccordance with aspects of the present subject matter;

FIG. 3 illustrates a side view of an outboard portion of the rotor bladeshown FIG. 2, particularly illustrating a blade root of the rotor blade;

FIG. 4 illustrates a top view of the blade root shown in FIG. 3; and,

FIG. 5 illustrates a partial side view of a wind turbine having therotor blade shown in FIGS. 2-4 installed thereon.

DETAILED DESCRIPTION OF THE INVENTION

Reference now will be made in detail to embodiments of the invention,one or more examples of which are illustrated in the drawings. Eachexample is provided by way of explanation of the invention, notlimitation of the invention. In fact, it will be apparent to thoseskilled in the art that various modifications and variations can be madein the present invention without departing from the scope or spirit ofthe invention. For instance, features illustrated or described as partof one embodiment can be used with another embodiment to yield a stillfurther embodiment. Thus, it is intended that the present inventioncovers such modifications and variations as come within the scope of theappended claims and their equivalents.

In general, the present subject matter is directed to a rotor blade fora wind turbine having an angled blade root. In particular, the bladeroot of the rotor blade may define a planar end surface oriented at anangle relative to the longitudinal axis of the rotor blade. Accordingly,when the rotor blade is installed onto a wind turbine hub, an increasein the amount of tower clearance defined between the rotor blade and thewind turbine tower may be achieved. Such increased tower clearance mayallow for longer and/or lighter rotor blades to be utilized on a windturbine, thereby increasing the efficiency and/or output of the windturbine and/or decreasing the costs required to manufacture each rotorblade.

Referring now to the drawings, FIG. 1 illustrates perspective view ofone embodiment of a wind turbine 10. As shown, the wind turbine 10includes a tower 12 extending from a support surface 14, a nacelle 16mounted on the tower 12, and a rotor 18 coupled to the nacelle 16. Therotor 18 includes a rotatable hub 20 and at least one rotor blade 22coupled to and extending outwardly from the hub 20. For example, in theillustrated embodiment, the rotor 18 includes three rotor blades 22.However, in an alternative embodiment, the rotor 18 may include more orless than three rotor blades 22. Each rotor blade 22 may be spaced aboutthe hub 20 to facilitate rotating the rotor 18 to enable kinetic energyto be transferred from the wind into usable mechanical energy, andsubsequently, electrical energy. For instance, the hub 20 may berotatably coupled to an electric generator (not shown) positioned withinthe nacelle 16 to permit electrical energy to be produced.

Referring now to FIGS. 2-4, one embodiment of a rotor blade 100 havingan angled blade root 102 is illustrated in accordance with aspects ofthe present subject matter. In particular, FIG. 2 illustrates aperspective view of the rotor blade 100. FIG. 3 illustrates a side viewof an inboard portion of the rotor blade 100 shown in FIG. 2,particularly illustrating the blade root 102 of the rotor blade 100.Additionally, FIG. 4 illustrates a top view of the blade root 102 shownin FIG. 3.

As shown, the rotor blade 100 generally includes a blade root 102 and ablade tip 104 disposed opposite the blade root 102. A body 106 of therotor blade 100 extends lengthwise along a longitudinal axis 108 betweenthe blade root 102 and the blade tip 104 and generally serves as theouter shell of the rotor blade 100. As is generally understood, the body106 may define an aerodynamic profile to enable the rotor blade 100 tocapture kinetic energy from the wind using known aerodynamic principles.Thus, the body 106 may generally include a pressure side 110 and asuction side 112 extending between a leading edge 114 and a trailingedge 116. Additionally, the rotor blade 100 may have a span 118 definingthe total length of the blade 100 between the blade root 102 and theblade tip 104 and a chord 120 defining the total length of the body 106between the leading edge 114 and the trailing edge 116. As is generallyunderstood, the chord 120 may vary in length with respect to the span118 as the rotor blade 100 extends from the blade root 102 to the bladetip 104. It should be readily appreciated that the longitudinal axis 108of the rotor blade 100 may extend parallel to the span 118.

As indicated above, the body 106 of the rotor blade 100 may generallydefine an aerodynamic profile or shape. For example, in severalembodiments, the body 106 may define an airfoil shaped cross-section,such as by defining a symmetrical or cambered airfoil-shapedcross-section. In addition, the rotor blade 100 may also beaeroelastically tailored. Aeroelastic tailoring of the rotor blade 100may entail bending of the blade 100 in a generally chordwise directionand/or in a generally spanwise direction. The chordwise directiongenerally corresponds to a direction parallel to the chord 120 of therotor blade 100. The spanwise direction generally corresponds to adirection parallel to the span 118 or longitudinal axis 108 of the rotorblade 100. Aeroelastic tailoring may further entail twisting of therotor blade 100, such as twisting the blade 100 in a generally chordwiseand/or spanwise direction.

Referring particularly to FIGS. 3 and 4, the blade root 102 of the rotorblade 100 may generally comprise a substantially cylindrically shapedmember extending outwardly from the aerodynamically shaped body 106 ofthe rotor blade 100. For example, as shown in FIG. 3, the blade root 102may extend from the body 106 along a longitudinal axis 122 orientedparallel to and/or coaxial with the longitudinal axis 108 of the rotorblade 100. In general, the blade root 102 may be configured to bemounted or otherwise attached to the hub 20 of a wind turbine 10. Forexample, as shown in FIG. 4, a plurality of stud or bolt holes 124 maybe defined through a planar end surface 126 of the blade root 102 forreceiving a corresponding number of studs or bolts (not shown). As isgenerally understood, the studs or bolts may be used to attach the bladeroot 102 to a pitch bearing 128 (FIG. 5) disposed within and/or coupledto the hub 20. For instance, the blade root 102 may be configured to berigidly attached to the pitch bearing 128 such that the end surface 126contacts against and extends parallel to a corresponding surface of thepitch bearing 128. However, it should be appreciated by those ofordinary skill in the art that the blade root 102 may be attached to thehub 20 using any other suitable means and/or attachment method known inthe art.

It should be appreciated that, several embodiments, the blade root 102may be formed integrally with the body 106 of the rotor blade 100.Alternatively, the blade root 102 may comprise a separate componentconfigured to be separately attached to the body 106.

As particularly shown in FIG. 3, in accordance with several embodimentsof the present subject matter, the end surface 126 of the blade root 102may be oriented at an at an angle 130 relative to the rotor blade 100.Specifically, the end surface 126 may be configured such that an angle130 is defined between the end surface 126 and a reference plane 132extending perpendicular to the longitudinal axis 108 of the rotor blade100 and/or the longitudinal axis 122 of the blade root 102. As such,when the blade root 102 is attached to the hub 20 of a wind turbine 10,the longitudinal axis 108, 122 of the rotor blade 100 and/or the bladeroot 102 may be oriented at a non-perpendicular angle relative to theinterface defined between the end surface 126 and the pitch bearing 128.It should be appreciated that, as used herein, the term “referenceplane” corresponds to an imaginary plane defined perpendicular to thelongitudinal axis 108, 122 of the rotor blade 100 and/or the blade root102 and extending parallel to the chord 120 of the rotor blade 100.

In general, the angle 130 defined between the end surface 126 of theblade root 102 and the reference plane 132 may comprise any suitableangle greater than 0 degrees. However, in several embodiments, the angle130 may range from greater than 0 degrees to less than about 10 degrees,such as from about 0.5 degrees to about 5 degrees or from about 0.5degrees to about 3 degrees or from about 0.5 degrees to about 2 degreesor from about 1 degree to about 2 degrees and all other subrangestherebetween.

In several embodiments, the planer end surface 126 may be defined in theblade root 102 such that the end surface 126 is angled towards thepressure side 110 of the rotor blade 100. For example, as shown in FIG.3, the plane defined by the end surface 126 may be angled inwardlybetween a first edge 134 defined on the suction side 112 of the rotorblade 100 and a second edge 136 defined on the pressure side 110 of therotor blade 100, with the first edge 134 generally corresponding to thepoint on the end surface 126 disposed furthest away from the blade tip104 of the rotor blade 100 and the second edge 136 generallycorresponding to the point on the end surface 126 disposed closest tothe blade tip 104. As such, when the rotor blade 100 is installed on awind turbine hub 20, the rotor blade 100 may be angled away from thetower 12. Moreover, in one embodiment, the end surface 126 may bedefined in the blade root 102 such a centerline 138 defined halfwaybetween the first and second edges 134, 136 is generally aligned withand extends parallel to the chord 120 of the rotor blade 100.Accordingly, the tower clearance defined between the rotor blade 100 andthe tower 12 may be maximized when the blade 100 is pitched to its powerposition during operation (i.e., a position at which the pressure side110 of the rotor blade 100 faces directly into the wind).

It should be appreciated that the end surface 126 of the blade root 102may be formed using any suitable manufacturing method and/or means knownin the art. For instance, in several embodiments, the blade root 102 maybe initially formed having an end surface oriented substantiallyperpendicularly to the longitudinal axis 108, 122 of the rotor blade 100and/or the blade root 102 (i.e., substantially parallel to the referenceplane 132). In such embodiment, the angled end surface 126 may be formedby cutting, grinding or otherwise removing portions of the blade root102 using any suitable cutting, grinding and/or machining equipment.Alternatively, the blade root 102 may be initially formed having theangled end surface 126.

Referring now to FIG. 5, there is illustrated one embodiment of therotor blade 100 shown in FIGS. 2-4 installed on a wind turbine hub 20.Specifically, FIG. 5 illustrates the difference in tower clearance 144,146 achieved through the use of the disclosed rotor blade 100 ascompared to a conventional rotor blade 22 (indicated by dashed lines).As shown, when the blade root 102 of the disclosed rotor blade 100 issecured to the hub 20 (e.g., by securing the end surface 126 to aportion of the pitch bearing 128), the interface defined between the endsurface 126 and the hub 20 is oriented at a non-perpendicular anglerelative to the longitudinal axis 108 of the rotor blade 100. Thus, dueto the angled interface, the rotor blade 100 may be configured to extendoutwardly away from the tower 12. In contrast, when the blade root 140of a conventional rotor blade 22 is secured to the hub 20, the interfacedefined between the rotor blade 22 and the hub 20 is orientedperpendicular to the longitudinal axis 142 of the blade 22 and, thus,the rotor blade 22 extends generally parallel to the tower 12.Accordingly, the tower clearance 144 defined between the disclosed rotorblade 100 and the tower 12 may be significantly higher than the towerclearance 146 defined between the conventional blade 22 and the tower12.

This written description uses examples to disclose the invention,including the best mode, and also to enable any person skilled in theart to practice the invention, including making and using any devices orsystems and performing any incorporated methods. The patentable scope ofthe invention is defined by the claims, and may include other examplesthat occur to those skilled in the art. Such other examples are intendedto be within the scope of the claims if they include structural elementsthat do not differ from the literal language of the claims, or if theyinclude equivalent structural elements with insubstantial differencesfrom the literal languages of the claims.

1. A rotor blade for a wind turbine, the rotor blade comprising: a bladeroot defining a planar end surface; a blade tip; a body extendingbetween the blade root and the blade tip, the body defining alongitudinal axis and including a pressure side and a suction sideextending between a leading edge and a trailing edge, wherein an angleis defined between the planar end surface and a reference planeextending perpendicular to the longitudinal axis, the angle beinggreater than 0 degrees and less than about 10 degrees.
 2. The rotorblade of claim 1, wherein the angle ranges from about 0.5 degrees toabout 5 degrees.
 3. The rotor blade of claim 1, wherein the angle rangesfrom about 0.5 degrees to about 3 degrees.
 4. The rotor blade of claim1, wherein the angle ranges from about 0.5 degrees to about 2 degrees.5. The rotor blade of claim 1, wherein the angle ranges from about 1degree to about 2 degrees.
 6. The rotor blade of claim 1, wherein theplanar end surface is angled towards the pressure side of the body. 7.The rotor blade of claim 1, wherein the planar end surface comprises afirst edge and a second edge, wherein a centerline defined between thefirst and second edges is aligned with a chord of the rotor blade.
 8. Awind turbine, comprising: a plurality of rotor blades, each of theplurality of rotor blades comprising: a blade root defining a planar endsurface; a blade tip; a body extending between the blade root and theblade tip, the body defining a longitudinal axis and including apressure side and a suction side extending between a leading edge and atrailing edge, wherein an angle is defined between the planar endsurface and a reference plane extending perpendicular to thelongitudinal axis, the angle being greater than 0 degrees and less thanabout 10 degrees.
 9. The wind turbine of claim 8, wherein the angleranges from about 0.5 degrees to about 5 degrees.
 10. The wind turbineof claim 8, wherein the angle ranges from about 0.5 degrees to about 3degrees.
 11. The wind turbine of claim 8, wherein the angle ranges fromabout 0.5 degrees to about 2 degrees.
 12. The wind turbine of claim 8,wherein the angle ranges from about 1 degree to about 2 degrees.
 13. Thewind turbine of claim 8, wherein the planar end surface is angledtowards the pressure side of the body.
 14. The wind turbine of claim 8,wherein the planar end surface comprises a first edge and a second edge,wherein a centerline defined between the first and second edges isaligned with a chord of the rotor blade.
 15. The wind turbine of claim8, further comprising: a tower; a nacelle mounted on the tower; and, arotor coupled to the nacelle, the rotor including a rotatable hub,wherein the blade root of each of the plurality of rotor blades iscoupled to the hub such that each rotor blade extends away from thetower.
 16. A blade root for a wind turbine rotor blade, the blade rootcomprising: a substantially cylindrically shaped member extendinglengthwise along a longitudinal axis and defining a planar end surface,wherein an angle is defined between the planar end surface and areference plane extending perpendicular to the longitudinal axis, theangle being greater than 0 degrees and less than about 10 degrees. 17.The blade root of claim 16, wherein the angle ranges from about 0.5degrees to about 5 degrees.
 18. The blade root of claim 16, wherein theangle ranges from about 0.5 degrees to about 3 degrees.
 19. The bladeroot of claim 16, wherein the angle ranges from about 0.5 degrees toabout 2 degrees.
 20. The blade root of claim 16, wherein the angleranges from about 1 degree to about 2 degrees.